A standard flow-control and shutoff valve of the type described in German patent document 3,107,431 of W. Orszullok or in commonly owned U.S. patent application Ser. No. 07/580,939 filed 10 Sept. 1990 has a housing forming a compartment traversed by an axis and having a radially opening outlet port and an axially open inlet port. Fluid can flow through the compartment in a flow direction from the inlet port to the outlet port in the open condition of the valve. A valve plate fixed in the housing is formed relative to the flow direction with a flat upstream face and with an axially throughgoing valve orifice opening at the face and a control plate rotatable in the housing about the axis is formed relative to the flow direction with a flat downstream face riding on the valve-plate face, with an axially throughgoing control orifice opening at the face. This control plate is pivotal on the valve plate about the axis for alignment of the orifices and flow through the valve from the inlet port to the outlet port and for misalignment of the orifices for restricted flow from the inlet port to the outlet port. A combined spring and seal fitted into the inlet port typically press the downstream face of the control plate against the upstream face of the valve plate. The control plate is operated by a valve stem rotatable in the housing about the axis and formed at its inner end with a noncircular projection passing through the control plate and fitting in a complementary recess formed on the downstream face of the control plate.
As a rule, the housing is externally threaded, typically with a 1/2 inch standard pipe thread, so that it can be screwed directly into a complementarily threaded hole in a fixture such as a faucet that incorporates the valve. The stem itself must be of large enough diameter that a handle or knob can be mounted on it. Thus little room is left in the housing for flow from the inlet port to the outlet port. It is therefore necessary for the user to make the coupling projection of the valve stem as small as possible in order to minimize the size of the hole in the valve plate and the room it takes up in the flow chamber. The tradeoff is therefore between strength and flow cross section, so that it is rarely possible to achieve a high-volume flow with a valve engineered for a long service life.